I've been studying your design and from what I can see the guns have to be pivoted out on the rod in order to be removed. If this is the case why not concentrate on securing the hinge to prevent pivoting instead?
It seems to me that if each of those hinges was bored and secured with a good quality padlock it would prevent pivoting the gun to get it out.
Sure the locks could be cut but just how much time can a burglar spend before the police arrive?
Jim

The 2nd Amendment IS an unalienable right.